The subjects described above are generally known. Purely by way of example, reference is made to DE 42 43 045 A1 and JP 08 090 028 A.
In the case of multi-stand cold-rolling mills, the strip thickness is usually measured downstream from the first rolling stand and downstream from the last rolling stand of the cold-rolling mill train. Strip thickness defects which arise in the intermediate rolling stands of the cold-rolling mill train are not detected until the thickness measurement is carried out downstream from the last rolling stand of the cold-rolling mill train. Owing to the principles involved, the outlet-side monitoring of the cold-rolling mill train, which entails dead times, is only able to eliminate these defects incompletely. The elimination of the thickness defects is particularly difficult in so-called mode C, in which the last rolling stand of the cold-rolling mill train is operated as a skin-pass stand with a constant rolling force. The reason for this is that the monitoring acts on the last rolling stand for which the roll nip is controlled, i.e. on the penultimate rolling stand of the cold-rolling mill train. The dead time thus comprises the time which the strip needs in order to be transported from the penultimate rolling stand of the rolling mill train to the thickness measuring device. As a result, only very poor control dynamics are achievable. As already mentioned, in skin-pass mode C the last rolling stand of the multi-stand cold-rolling mill train is operated with a constant rolling force. For this purpose, the last rolling stand is screwed down with a controlled force. On account of the rolling force control, the last rolling stand reacts to thickness defects of the strip by correspondingly yielding. The strip thickness defects thus pass through the last rolling stand of the cold-rolling mill train undiminished. If required, the outlet-side monitoring, i.e. the thickness measuring device downstream from the cold-rolling mill train, changes the pass reduction of the penultimate rolling stand of the cold-rolling mill train. On account of the large amount of dead time between the control intervention on the penultimate rolling stand of the cold-rolling mill train and the subsequent measurement by means of the thickness measuring device, however, it is only possible to sufficiently eliminate infrequent defects.